40 CFR § 81.150 - Northern Piedmont Intrastate Air Quality Control Region.

The Northern Piedmont Intrastate Air Quality Control Region (North Carolina) consists of the territorial area encompassed by the boundaries of the following jurisdictions or described area (including the territorial area of all municipalities (as defined in section 302(f) of the Clean Air Act, 42 U.S.C. 1857h(f)) geographically located within the outermost boundaries of the area so delimited):

In the State of North Carolina: Alamance County, Caswell County, Davidson County, Davie County, Forsyth County, Guilford County, Randolph County, Rockingham County, Stokes County, Surry County, Yadkin County.